1. Field of the Invention
The present invention relates to the detection of electromagnetically differing materials. More particularly, the present invention relates to detection and tracking of welds, wires embedded in composite materials and seams on electric wires through the detection of variations in eddy currents generated in the material being examined.
2. Description of the Prior Art
Generally, the detection of seams in electric wire, wires embedded in composite materials or welds is an integral part of monitoring and managing process or quality control of a manufacturing process. More particularly, the tracking of electric resistance welds (ERWs) is an integral function of process control during the manufacture of ERW tubes. Maintaining alignment of equipment on a weld is a critical requirement, whether it is used to keep the weld centered beneath an annealing head, or to keep weld inspection sensors centered over the weld during the inspection process. Alignment is particularly important when the integrity of the welded area is tested using ultrasonic flaw detection techniques.
One prior art method of tracking welds consists of painting a stripe offset from the weld and then tracking the paint stripe using video cameras. This prior art process has drawbacks in that it is cumbersome, adds process steps and expense to the testing process.
Another prior art method for tracking welds uses a high frequency ultrasonic transducer in an attempt to delineate the weld zone by the backscatter induced by the grain structure of the weld itself. However, this process is limited because it does not produce consistent results.